CSS Drop Line Menu: Submenu

Hello all,
I am trying to setup this drop line menu so that the drop line appears on hover for the parent and under the parent li. But, I can’t seem to get the submenu to work with the submenu css styles. It is linking with the styles for the top level menu still. I have tried several different methods of nested styles, but can’t get it right. Now I can’t even hide the submenu until hover… What am I doing wrong? Can someone see what I am missing here?